Signal Guide

Service Description Selection TETRA

Here you will find information about the selected service, along with measurement examples.

TETRA Theory & Details
Communication
Typical Frequency Range:

380 – 400 and 410 – 430 MHz. Uplink at 380 – 390 and 410 – 420 MHz. Duplex spacing 10 MHz. Other frequencies used in Europe: 450 – 470 and 870 – 876 / 915 – 921 MHz.

General:

TETRA (Terrestrial Trunked Radio) is the successor to the analog networks used by security services.

Modulation: DQPSK, QAM

π/4-DQPSK, π/8-DQPSK, 4-QAM, 16-QAM, 64-QAM. Uplink: TDMA frame structure (time division multiple access) with four timeslots ach of about 14 ms. Downlink transmits continuously.

TETRA Measurement Examples
Spectrum
Shows a classic TETRA downlink signal. The lobe to the right of center is typical. The uplink has a similar spectrum but is keyed at 14/56 ms
Spectrogram
Same range as Spectrum. One FFT is written every 161 ms. Two weak emitters can be seen in the uplink at 381 MHz. Broadband interference is present briefly at -5 s
HiRes Spectrogram Full
Frequency range is limited to the downlink, time axis expanded to 39 ms. The modulation gaps (slight thinning of the lines) at -20 and -34 ms indicate a new timeslot (spacing 14 ms).
HiRes Spectrogram Zoom
Section from HiRes Spectrogram Full. The modulation gaps at -20 ms are shown enlarged; the arrows indicate the start of the gap. Modulation gaps occur synchronously for several stations.
Persistence Spectrum
Calculated from the same data as HiRes Spectrogram Full. Shows the frequency of occurrence over 39 ms.
Magnitude
Time domain display based on the same data as HiRes Spectrogram Full. The modulation gaps at -20 and -34 ms can be seen. The gaps occur synchronously.
Scope